Silver nitrate is an inorganic compound with chemical formula AgNO 3. It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides.[citation needed] It was once called lunar caustic because silver was called luna by ancient alchemists who associated silver with the moon.[7] In solid silver nitrate, the silver ions are three-coordinated in a trigonal planar arrangement.[4]